(Technical Field)
The present disclosure relates to a collision determination apparatus in which a possibility of collision between an own vehicle and another vehicle is determined through a wireless communication performed by the apparatuses mounted on each of the vehicles, and a pseudo range information apparatus.
(Description of the Related Art)
In recent years, an inter-vehicle communication system has been proposed, in which each of a plurality of vehicles transmits communication packets each indicating vehicle information such as travelling speed of the own vehicle, current location and travelling direction, and subsequently receives packets transmitted from other vehicle.
As an apparatus used for such an inter-vehicle communication system, JP-A-2012-22671 discloses an apparatus that determines, based on positional information of the other vehicle obtained by the inter-vehicle communication and the positional information of the own vehicle, whether or not the own vehicle is likely to collide with other vehicle (hereinafter referred to as a collision determination apparatus).
More specifically, the above-mentioned collision determination apparatus disclosed in the above-described patent document determines, based on a relative speed of the other vehicle with respect to the own vehicle, a relative travelling direction, and a positional relationship between the own vehicle and the other vehicle, whether or not the own vehicle is likely to collide with an object other vehicle. The vehicle which is likely to collide with the own vehicle is defined as other vehicle having a relative distance which tends to decrease with respect to the own vehicle. For convenience, a relationship having mutual relative distances being decreased is referred to as an approaching relationship.
When the collision determination apparatus determines that the other vehicle is likely to collide with the own vehicle, the collision determination apparatus calculates, based on the above-described various information, a collision margin time which is a remaining time to collision (hereinafter referred to as TTC: Time to Collision). In the case where the TTC is less than a predetermined threshold, the collision determination apparatus issues an alert to the driver of the own vehicle.
It should be noted that the current locations of the respective vehicles can be identified by receiving radio waves from satellites (hereinafter referred to as GNSS satellites) used for a global navigation satellite system, i.e., GNSS. Generally, to identify the current location by using the radio waves transmitted from the GNSS satellite, radio waves transmitted by 4 or more GNSS satellites have to be captured.
According to related art disclosed in the above-mentioned patent document, to calculate the TTC relative to other vehicle, each of the own vehicle and other vehicle is required to complete a measurement of their current location (i.e., positioning) before calculating the TTC. To measure the current location, as described above, at least 4 GNSS satellites have to be captured.
Therefore, when the number of captured GNSS satellites is 3 or less, positioning cannot be accomplished so that the above-mentioned TTC cannot be calculated.
In this case, the apparatus cannot determine a possible approaching relationship between other vehicle and the own vehicle being communicated via an inter-vehicle communication.